In stringed musical instruments such as guitars and the like, string tensioning adjustment is normally provided at one end of the instrument while at the other end the strings are bent over a bridge to a tailpiece where the strings are anchored; thus, with the strings tensioned against the bridge, the end point of the active region of string vibration is defined by the longitudinal location of the bridge. This is critical, relative to the frets on the fingerboard, for good intonation and true octaves.
Setting the height of each string above the keyboard involves a tradeoff between ease of fingering and the maximum available amplitude at the onset of "buzzing" of the string against the fingerboard. The optimum string height is not uniform from string to string: it varies according to the string material, type (round-wound or solid), diameter and tension.
Similarly the optimum longitudinal location for the bridge varies from string to string.
For these and other reasons, many instrument manufacturers and musicians value and seek the capability of setting the string height and the longitudinal bridge location independently for each string.
Along with requirements of elegance and producibility, the structure of the bridge and the tailpiece should made as stable as possible to minimize variations in tuning and playing characteristics.
The bridge should provide a well-defined support point which, by not absorbing vibrational energy from the strings, allows them to vibrate freely with full tonal quality and long sustain.
Many conventional instruments are designed such that there is an inherent structural dependence on body material such as wood or plastic, interposed between the bridge and the tailpiece, with a resultant risk of tuning variations due to dimensional instability.